nanog mailing list archives
Re: IPv6 isn't SMTP
From: Lamar Owen <lowen () pari edu>
Date: Thu, 27 Mar 2014 10:23:10 -0400
On 03/26/2014 08:12 PM, Jimmy Hess wrote:
Tell that to the 100,000+ e-mails I blocked last week (and the several hundred that got through before I was able to get all the blocks entered into my ingress ACLs) from proper rDNS addresses where the addresses were hopping all over a /24, a /22, three /21's, four /20's, and six /19s in widely separated blocks. Every single address in those blocks eventually attempted to send e-mail, and every address had proper rDNS for the pseudorandom domain names, mostly in the .in TLD, but some others, too (the blocks were all over, with some registed through ARIN, some through RIPE, some through AfriNIC, and some through APNIC, with hosters in Europe, North and South America, Asia, and Africa.) Note that these passed full FCrDNS verification in postfix. They all had very similar characteristics, including an embedded image payload/ad and a couple of hundred kB of anti-Bayesian text, including the full text of Zilog's Z80 manual at one point.As far as i'm concerned.... if you can force the spammer to use their own IP range, that they can setup RDNS for, then you have practically won, for all intents and purposes, as it makes blacklisting feasible, once again! Spammers can jump through these hoops --- but spammers aren't going to effectively scale up their spamming operation by using IP address ranges they can setup RDNS on.
Of course, the other tens of thousands per day that get blocked for not having rDNS from residential bots make the case for leaving rDNS (and the FCrDNS variant) turned on, but it is not a cure-all.
Current thread:
- Re: IPv6 isn't SMTP, (continued)
- Re: IPv6 isn't SMTP Blake Hudson (Mar 26)
- Re: IPv6 isn't SMTP Jimmy Hess (Mar 26)
- Re: IPv6 isn't SMTP Blake Hudson (Mar 27)
- Re: IPv6 isn't SMTP Barry Shein (Mar 27)
- Re: IPv6 isn't SMTP Blake Hudson (Mar 27)
- Re: IPv6 isn't SMTP Barry Shein (Mar 27)
- Re: IPv6 isn't SMTP Blake Hudson (Mar 28)
- Re: IPv6 isn't SMTP Clay Fiske (Mar 27)
- Re: IPv6 isn't SMTP Blake Hudson (Mar 28)
- Re: IPv6 isn't SMTP Dave Crocker (Mar 27)
- Re: IPv6 isn't SMTP Lamar Owen (Mar 27)
- Re: IPv6 isn't SMTP James R Cutler (Mar 26)
- Re: IPv6 isn't SMTP John Levine (Mar 26)
- Re: IPv6 isn't SMTP Tony Finch (Mar 27)
- Re: IPv6 isn't SMTP Enno Rey (Mar 27)
- Re: IPv6 isn't SMTP John R. Levine (Mar 27)
- Re: IPv6 isn't SMTP Robert Drake (Mar 26)
- Re: IPv6 address literals probably aren't SMTP either John Levine (Mar 26)
- Re: IPv6 address literals probably aren't SMTP either Robert Drake (Mar 26)